In some catheterization procedures, it is desirable to use a series of sequentially placed catheters. For example, in percutaneous transluminal coronary angioplasty procedures, in which a balloon catheter is advanced into a stenosed region of the patient's coronary artery and is inflated within the stenosis to dilate the lumen of the artery, it is not uncommon for the physician to require the sequential use of several balloon dilatation catheters having balloons of progressively increasing size. Typically, such catheters are used in connection with a guidewire that extends through the catheter and serves as a guide along which the catheter may be advanced to the stenosis. When performing such a catheter exchange, it is important to do so without significantly shifting the position of the guidewire so that the guidewire may be used to guide the next catheter to the stenosis. In order to maintain guidewire position, conventional practice has been to use a relatively long exchange wire. The exchange wire, which typically is of the order of 300 cm long (as compared to a conventional guidewire length of the order of 175 cm) is first exchanged for the conventional guidewire by removing the conventional guidewire from the indwelling catheter and replacing it with the longer exchange wire. Then the indwelling catheter is withdrawn over the exchange wire, the exchange wire being sufficiently long so that it is never completely covered by the withdrawn catheter, thereby enabling the exchange wire to be held in position by the physician or an assistant during the catheter withdrawal. After the initial catheter is removed, the succeeding catheter is advanced over the exchange wire which guides the second catheter to the stenosis. The exchange wire then may be removed and may be replaced with a conventional length guidewire which, typically, will be more easily manipulated during the continuing angioplasty procedure.
The foregoing procedures are time consuming and somewhat awkward. A significant advance in the technique for effecting catheter exchanges has been developed and has been in use enables exchange of catheters without using separate exchange wires. That system utilizes an extension wire that is attached to the proximal end of the indwelling conventional guidewire. That effectively extends the overall length of the guidewire to that needed for the catheter exchange. The system uses a connection in which the distal end of an extension wire is telescopically connected with the proximal end of the guidewire.
In one such system described in U.S. patent application Ser. No. 07/206,008 filed Jun. 13, 1988, now U.S. Pat. No. 5,133,364, a connection system for a guidewire and guidewire extension utilizes a telescoping connector that is self-latching, disconnectible and reconnectible without deformation of the guidewire or the extension. The connection enables the guidewire extension to be attached for a catheter exchange, then disconnected after the catheter exchange is complete to permit the guidewire and catheter to be manipulated and operated conventionally. Should another catheter exchange be required, the extension wire, which may be reused, is simply reconnected to the proximal end of the guidewire and the catheter exchange procedure may be repeated. The number of guidewire-extension wire connections and disconnections is unlimited as is the number of catheter exchanges that may be performed with the system. More particularly, the guidewire is provided with a tubular socket on the proximal end. The extension wire includes a shaft having a distal end that is dimensioned to be received in the socket. A segment of the distal end of the shaft is surrounded by a helical coil, preferably formed from rectangular cross-section wire. The coil is attached to the extension wire shaft at the distal end of the coil but is free at the proximal end of the coil to enable the coil to stretch and contract about the shaft. The distal end of the extension wire carrying the coil is easily insertable into the socket on the proximal end of the guidewire but self-locks in the socket and cannot be easily withdrawn. The extension wire and guidewire may be disconnected easily, however, by twisting the guidewire extension while simultaneously withdrawing it axially from the socket. The twisting motion frees the locking engagement of the helical coil with the internal surface of the socket.
Although the above-described self-latching reconnectible guidewire system has been used widely by physicians, it would be desirable to improve the convenience of the device. In particular, it is common for guidewires to come in several different diameters, each such guidewire presenting somewhat different operational characteristics. Among the most common diameters for steerable coronary guidewires are those having outer diameters of 0.012" and 0.014". The sockets on the proximal ends of the 0.012" and 0.014" guidewires have different inner diameters and, therefore, each requires a differently dimensioned connector coil on its associated extension wire. Consequently, a separate extension wire must be used with each separate diameter guidewire. That, in turn, requires that different size extension wires be stocked and in readiness for use by the physician. It would be desirable, therefore, to provide an extension wire usable universally with both sizes of guidewires.